Biology Regents Practice Exam

How does botulinum toxin affect nerve cell communication?

1. It alters the DNA structure.

2. It inhibits ATP production.

3. It blocks a signaling molecule necessary for communication.

4. It disrupts digestive hormone levels.

The correct answer is: It blocks a signaling molecule necessary for communication.

Botulinum toxin primarily affects nerve cell communication by blocking the release of a neurotransmitter called acetylcholine. This neurotransmitter is essential for transmitting signals from nerve cells to muscles, enabling muscle contraction and movement. The toxin affects the synaptic vesicles in the nerve endings, preventing their fusion with the cell membrane, which is necessary for the release of acetylcholine into the synaptic cleft. When acetylcholine release is inhibited, the muscle fibers cannot receive the signals needed for contraction, leading to paralysis. This mechanism underlies the toxin's potency and why it can be dangerous in the context of food poisoning, as it disrupts normal neuromuscular function. The other options involve different mechanisms that do not directly pertain to how botulinum toxin operates. Altering DNA structure does not relate to the action of the toxin, and while ATP production is crucial for many cellular processes, its inhibition is not the primary mechanism by which botulinum toxin exerts its effects. Disruption of digestive hormone levels is also not relevant to the specific action of botulinum toxin on nerve communication.